Thermodynamics behaviour of Germanium during equilibrium reactions between FeOx-CaO-SiO2-MgO slag and molten copper

Thermodynamics Behaviour of Germanium during Equilibrium Reactions between FeOx-CaO-SiO2-MgO Slag and Molten Copper M.A.H. Shuva1,2, M.A. Rhamdhani1,2,*, G.A. Brooks1,2, S. Masood1,2, M.A. Reuter3 1Swinburne University of Technology, Melbourne, Australia 2Wealth from Waste Research Cluster, Australia 3Helmholtz Institute Freiberg for Resource Technology, Germany *Corresponding author: ARhamdhani@swin.edu.au ABSTRACT The distribution ratio of germanium (Ge), LGe /, during equilibrium reactions between magnesia saturated FeOx-CaO-SiO2 (FCS) slag and molten copper has been measured under oxygen partial pressures from 10-10 to 10-7 atm and at temperatures 1473 to 1623 K (1200 to 1350oC). It was observed that the Ge distribution ratio increases with increasing oxygen partial pressure, and with decreasing temperature. It was also observed that the distribution ratio is strongly dependant on slag basicity. The distribution ratio was observed to increase with increasing optical basicity. At fixed CaO concentration in the slag, the distribution ratio was found to increase with increasing Fe/SiO2 ratio, tending to a plateau at LGe / = 0.8. This behaviour is consistent with the assessment of ionic bond fraction carried out in this study, and suggested the acidic nature of germanium oxide (GeO2) in the slag system studied. The characterisation results of the quenched slag suggested that Ge is present in the FeOx-CaO- SiO2-MgO slag predominantly as GeO2. At 1573 K (1300oC) and pO2 = 10-8 atm, the activity coefficient of GeO2 in the slag was calculated to be in the range of 0.24 to 1.50. The results from the current study suggested that less-basic slag, high operating temperature, and low oxygen partial pressure promote a low Ge distribution ratio. These conditions are desired for maximising Ge recovery, for example during pyrometallurgical processing of Ge-containing e-waste through secondary copper smelting. Overall, the thermodynamics data generated from this study can be used for process modelling purposes for improving recovery of Ge in primary and secondary copper smelting processes